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    <div class="post-body" itemprop="articleBody"><p>本文主要是网络编程——多路复用IO中的epoll的相关笔记，若笔记中有错误或者不合适的地方，欢迎批评指正😃。</p>
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<details class="folding-tag" blue><summary> 点击查看使用工具及版本 </summary>
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              <table>    <tr>        <td align="center" width=150px>Windows</td>        <td align="left">windows11</td>    </tr>    <tr>        <td align="center">Ubuntu</td>        <td align="left">Ubuntu16.04的64位版本</td>      </tr>    <tr>        <td align="center">VMware® Workstation 16 Pro</td>        <td align="left">16.2.3 build-19376536</td>      </tr>    <tr>        <td align="center">SecureCRT</td>        <td align="left">Version 8.7.2 (x64 build 2214)   -   正式版-2020年5月14日</td>      </tr>    <tr>        <td align="center">开发板</td>        <td align="left">正点原子 i.MX6ULL Linux阿尔法开发板</td>      </tr>    <tr>        <td align="center">uboot</td>        <td align="left">NXP官方提供的uboot，NXP提供的版本为uboot-imx-rel_imx_4.1.15_2.1.0_ga(使用的uboot版本为U-Boot 2016.03)</td>      </tr>    <tr>        <td align="center">linux内核</td>        <td align="left">linux-4.15(NXP官方提供)</td>      </tr>    <tr>        <td align="center">STM32开发板</td>        <td align="left">正点原子战舰V3(STM32F103ZET6)</td>      </tr></table>
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<details class="folding-tag" blue><summary> 点击查看本文参考资料 </summary>
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              <table>    <tr><td align="center">参考方向  </td><td align="center">参考原文</td></tr>    <tr><td align="center">---</td><td align="left"><a href="" target="_blank">--- <i class="fa fa-external-link-alt"></i> </a></td></tr></table> 
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<h1 id="一、epoll简介"><a href="#一、epoll简介" class="headerlink" title="一、epoll简介"></a><font size=3>一、<code>epoll</code>简介</font></h1><p><code>epoll</code>是在<code>2.6</code>内核中提出的，是之前的<code>select</code>和<code>poll</code>的增强版本。相对于<code>select</code>和<code>poll</code>来说，<code>epoll</code>更加灵活，没有描述符限制，它所支持的文件描述符上限是整个系统可以打开的文件数目。</p>
<p><code>epoll</code>使用一个文件描述符管理多个描述符，将用户关系的文件描述符的事件存放到内核的一个事件表中，并且每个<code>fd</code>上边都会有一个<code>callback</code>函数（回调函数），只有活跃的<code>socket</code>才会去主动调用这个回调函数，这属于一种<strong>通知机制</strong>，就是当事件发生的时候，则主动通知；通知机制的反面，就是轮询机制。</p>
<p>我们主要会用到以下三个函数，这里提前说一下，后边介绍原理的话可能会用到：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="type">int</span> <span class="title function_">epoll_create</span><span class="params">(<span class="type">int</span> size)</span>;</span><br><span class="line"><span class="type">int</span> <span class="title function_">epoll_ctl</span><span class="params">(<span class="type">int</span> epfd, <span class="type">int</span> op, <span class="type">int</span> fd, <span class="keyword">struct</span> epoll_event *event)</span>;</span><br><span class="line"><span class="type">int</span> <span class="title function_">epoll_wait</span><span class="params">(<span class="type">int</span> epfd, <span class="keyword">struct</span> epoll_event *events, <span class="type">int</span> maxevents, <span class="type">int</span> timeout)</span>;</span><br></pre></td></tr></table></figure>

<p><code>epoll</code>通过以上三个函数把原先的<code>select/poll</code>调用分成了<code>3</code>个部分：</p>
<ul>
<li>（1）调用<code>epoll_create()</code>建立一个<code>epoll</code>对象(在<code>epoll</code>文件系统中为这个句柄对象分配资源)；</li>
<li>（2）调用<code>epoll_ct()l</code>向<code>epoll</code>对象中添加需要连接的<code>socket</code>套接字；</li>
<li>（3）调用<code>epoll_wait()</code>收集发生的事件的连接。</li>
</ul>
<blockquote>
<p>这样做的好处？</p>
</blockquote>
<p>假设现在有<code>100</code>万个客户端同时与一个服务器进程保持着<code>TCP</code>连接。而每一时刻，通常只有几百或者几千个<code>TCP</code>连接是活跃的，这种情况下如何实现高并发？</p>
<p>在<code>select/poll</code>时代，服务器进程每次都把这<code>100</code>万个连接告诉操作系统(从用户态复制句柄数据结构到内核态)，让操作系统内核去查询这些套接字上是否有事件发生，轮询完后，再将句柄数据复制到用户态，让服务器应用程序轮询处理已发生的网络事件，这一过程资源消耗较大。对于<code>select</code>来说，在<code>FD_SETSIZE</code> 为<code>1024</code>的情况下，则我们至少需要创建<code>1k</code>个进程才能实现<code>100</code>万的并发连接。除了进程间上下文切换的时间消耗外，从内核&#x2F;用户空间大量的无脑内存拷贝、数组轮询等，是系统难以承受的。因此，基于<code>select</code>模型的服务器程序，要达到<code>100</code>万级别的并发访问，是一个很难完成的任务。<code>poll</code>与<code>select</code>其实是很类似的，它也是难以完成这样的高并发连接。</p>
<p>而我们使用<code>epoll</code>的话，只需要在进程启动时建立一个<code>epoll</code>对象，然后在需要的时候向这个<code>epoll</code>对象中添加或者删除连接。同时，<code>epoll_wait</code>的效率也非常高，因为调用<code>epoll_wait</code>时，并不会一次性向操作系统复制这<code>100</code>万个连接的句柄数据，内核也不需要去遍历全部的连接。</p>
<h1 id="二、epoll数据结构"><a href="#二、epoll数据结构" class="headerlink" title="二、epoll数据结构"></a><font size=3>二、<code>epoll</code>数据结构</font></h1><p>关于<code>epoll</code>的源码我是找了一下，但是没有找到，也可能是自己查找的方式不对吧，但是这个嘛暂时不太重要，后边再补充吧。不过我在<code>github</code>上找到了一个项目，包含了<code>linux</code>内核源码：<a target="_blank" rel="noopener" href="https://github.com/torvalds/linux/blob/master/fs/eventpoll.c">linux&#x2F;eventpoll.c at master · torvalds&#x2F;linux (github.com)  <i class="fa fa-external-link-alt"></i></a></p>
<p>先来看一张网上找到的一张关于<code>epoll</code>数据结构的图，不过我修改成自己可以理解的样子啦（这里会提到红黑树，前边学习数据结构的时候好像没有了解这一种树，后边会在数据结构的笔记中补充）：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/01HQ%E8%AF%BE%E7%A8%8B%E4%BD%93%E7%B3%BB/LV06-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B/LV06-03-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B-07-%E5%A4%9A%E8%B7%AF%E5%A4%8D%E7%94%A8IO-03-epoll/img/image-20220704074731164.png" alt="image-20220704074731164" style="zoom:50%;" />



<p>当某一进程调用<code>epoll_create()</code>创建<code>epoll</code>对象的时候，<code>Linux</code>内核会创建一个<code>eventpoll</code>结构体，这个结构体中有两个成员与<code>epoll</code>的使用方式密切相关，这两个成员是<code>rdllist</code>和<code>rbr</code>，这两个成员的类型如下所示：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">eventpoll</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	...</span><br><span class="line">	<span class="comment">/* List of ready file descriptors */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">list_head</span> <span class="title">rdlist</span>;</span></span><br><span class="line">    ...</span><br><span class="line">    <span class="comment">/* RB tree root used to store monitored fd structs */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">rb_root_cached</span> <span class="title">rbr</span>;</span></span><br><span class="line">	...</span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure>

<ul>
<li><p><code>rdlist</code>：该成员中存放的是将要通过<code>epoll_wait</code>返回给用户的满足条件的事件，这些事件被存储在一个<strong>双向链表</strong>中，而<code>rdlist</code>存放的就是这个双向链表的<strong>首地址</strong>。</p>
</li>
<li><p><code>rbr</code>：该成员中存放的是红黑树的<strong>根节点</strong>，这颗树中存储着所有添加到<code>epoll</code>中的需要监控的事件。</p>
</li>
</ul>
<details class="folding-tag" blue><summary> 点击查看 eventpoll 详细定义 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/*</span></span><br><span class="line"><span class="comment"> * This structure is stored inside the &quot;private_data&quot; member of the file</span></span><br><span class="line"><span class="comment"> * structure and represents the main data structure for the eventpoll</span></span><br><span class="line"><span class="comment"> * interface.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">eventpoll</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	<span class="comment">/*</span></span><br><span class="line"><span class="comment">	 * This mutex is used to ensure that files are not removed</span></span><br><span class="line"><span class="comment">	 * while epoll is using them. This is held during the event</span></span><br><span class="line"><span class="comment">	 * collection loop, the file cleanup path, the epoll file exit</span></span><br><span class="line"><span class="comment">	 * code and the ctl operations.</span></span><br><span class="line"><span class="comment">	 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">mutex</span> <span class="title">mtx</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* Wait queue used by sys_epoll_wait() */</span></span><br><span class="line">	<span class="type">wait_queue_head_t</span> wq;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* Wait queue used by file-&gt;poll() */</span></span><br><span class="line">	<span class="type">wait_queue_head_t</span> poll_wait;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* List of ready file descriptors */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">list_head</span> <span class="title">rdllist</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* Lock which protects rdllist and ovflist */</span></span><br><span class="line">	<span class="type">rwlock_t</span> lock;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* RB tree root used to store monitored fd structs */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">rb_root_cached</span> <span class="title">rbr</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/*</span></span><br><span class="line"><span class="comment">	 * This is a single linked list that chains all the &quot;struct epitem&quot; that</span></span><br><span class="line"><span class="comment">	 * happened while transferring ready events to userspace w/out</span></span><br><span class="line"><span class="comment">	 * holding -&gt;lock.</span></span><br><span class="line"><span class="comment">	 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">epitem</span> *<span class="title">ovflist</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* wakeup_source used when ep_scan_ready_list is running */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">wakeup_source</span> *<span class="title">ws</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* The user that created the eventpoll descriptor */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">user_struct</span> *<span class="title">user</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">file</span> *<span class="title">file</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* used to optimize loop detection check */</span></span><br><span class="line">	u64 gen;</span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">hlist_head</span> <span class="title">refs</span>;</span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">ifdef</span> CONFIG_NET_RX_BUSY_POLL</span></span><br><span class="line">	<span class="comment">/* used to track busy poll napi_id */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">int</span> napi_id;</span><br><span class="line"><span class="meta">#<span class="keyword">endif</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">ifdef</span> CONFIG_DEBUG_LOCK_ALLOC</span></span><br><span class="line">	<span class="comment">/* tracks wakeup nests for lockdep validation */</span></span><br><span class="line">	u8 nests;</span><br><span class="line"><span class="meta">#<span class="keyword">endif</span></span></span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<p>每一个<code>epoll</code>对象都会有一个独立的<code>eventpoll</code>结构体，用于存放通过<code>epoll_ctl</code>方法向<code>epoll</code>对象中添加进来的事件。这些事件都会挂载在红黑树中，这样的话，重复添加的事件就可以通过红黑树而高效的识别出来（红黑树的插入时间效率是<code>lg(n)</code>，其中<code>n</code>为树的高度）。</p>
<p>所有添加到<code>epoll</code>中的事件都会与设备（网卡）驱动程序建立回调关系，也就是说，当相应的事件发生时会调用这个回调方法。这个回调方法在内核中叫<code>ep_poll_callback</code>，它会将发生的事件添加到<code>rdlist</code>双链表中。</p>
<p>在<code>epoll</code>中，对于每一个事件，都会建立一个<code>epitem</code>结构体，其中有两个成员：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">epitem</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	<span class="class"><span class="keyword">union</span></span></span><br><span class="line"><span class="class">	&#123;</span></span><br><span class="line">		<span class="comment">/* RB tree node links this structure to the eventpoll RB tree */</span></span><br><span class="line">		<span class="class"><span class="keyword">struct</span> <span class="title">rb_node</span> <span class="title">rbn</span>;</span></span><br><span class="line">		<span class="comment">/* Used to free the struct epitem */</span></span><br><span class="line">		<span class="class"><span class="keyword">struct</span> <span class="title">rcu_head</span> <span class="title">rcu</span>;</span></span><br><span class="line">	&#125;;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* List header used to link this structure to the eventpoll ready list */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">list_head</span> <span class="title">rdllink</span>;</span></span><br><span class="line">	...</span><br><span class="line">&#125;; </span><br></pre></td></tr></table></figure>

<ul>
<li><code>rbn</code>：该成员表示挂载到<code>eventpoll</code> 的红黑树节点，这些节点存储着我们添加到<code>epoll</code>的所有事件。</li>
<li><code>rdllink</code>：该成员表示挂载到<code>eventpoll.rdllist</code>的节点，这些节点存储着已经准备好的事件。</li>
</ul>
<details class="folding-tag" blue><summary> 点击查看 epitem 详细定义 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/*</span></span><br><span class="line"><span class="comment"> * Each file descriptor added to the eventpoll interface will</span></span><br><span class="line"><span class="comment"> * have an entry of this type linked to the &quot;rbr&quot; RB tree.</span></span><br><span class="line"><span class="comment"> * Avoid increasing the size of this struct, there can be many thousands</span></span><br><span class="line"><span class="comment"> * of these on a server and we do not want this to take another cache line.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">epitem</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	<span class="class"><span class="keyword">union</span></span></span><br><span class="line"><span class="class">	&#123;</span></span><br><span class="line">		<span class="comment">/* RB tree node links this structure to the eventpoll RB tree */</span></span><br><span class="line">		<span class="class"><span class="keyword">struct</span> <span class="title">rb_node</span> <span class="title">rbn</span>;</span></span><br><span class="line">		<span class="comment">/* Used to free the struct epitem */</span></span><br><span class="line">		<span class="class"><span class="keyword">struct</span> <span class="title">rcu_head</span> <span class="title">rcu</span>;</span></span><br><span class="line">	&#125;;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* List header used to link this structure to the eventpoll ready list */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">list_head</span> <span class="title">rdllink</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/*</span></span><br><span class="line"><span class="comment">	 * Works together &quot;struct eventpoll&quot;-&gt;ovflist in keeping the</span></span><br><span class="line"><span class="comment">	 * single linked chain of items.</span></span><br><span class="line"><span class="comment">	 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">epitem</span> *<span class="title">next</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* The file descriptor information this item refers to */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">epoll_filefd</span> <span class="title">ffd</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* List containing poll wait queues */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">eppoll_entry</span> *<span class="title">pwqlist</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* The &quot;container&quot; of this item */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">eventpoll</span> *<span class="title">ep</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* List header used to link this item to the &quot;struct file&quot; items list */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">hlist_node</span> <span class="title">fllink</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* wakeup_source used when EPOLLWAKEUP is set */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">wakeup_source</span> __<span class="title">rcu</span> *<span class="title">ws</span>;</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* The structure that describe the interested events and the source fd */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">epoll_event</span> <span class="title">event</span>;</span></span><br><span class="line">&#125;; </span><br></pre></td></tr></table></figure>
              </div>
            </details>

<p>当调用<code>epoll_wait</code>检查是否有事件发生时，只需要检查<code>eventpoll</code>对象中的<code>rdlist</code>双链表中是否有<code>epitem</code>元素即可。如果<code>rdlist</code>不为空，则把发生的事件复制到用户态，同时将事件数量返回给用户。</p>
<p>总结下来就是，<strong>通过红黑树和双链表数据结构，并结合回调机制，使epoll更加高效。</strong></p>
<h1 id="三、相关API"><a href="#三、相关API" class="headerlink" title="三、相关API"></a><font size=3>三、相关<code>API</code></font></h1><h2 id="1-epoll-create"><a href="#1-epoll-create" class="headerlink" title="1. epoll_create()"></a><font size=3>1. <code>epoll_create()</code></font></h2><h3 id="1-1-函数说明"><a href="#1-1-函数说明" class="headerlink" title="1.1 函数说明"></a><font size=3>1.1 函数说明</font></h3><p>在<code>linux</code>下可以使用<code>man 2 epoll_create</code>命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">epoll_create</span><span class="params">(<span class="type">int</span> size)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数用于创建一个<code>epoll</code>句柄，也就是新创建一个<code>epoll</code>对象。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li><code>size</code>：<code>int</code>类型，在初始<code>epoll_create()</code>实现中，<code>size</code>参数告知内核调用者希望添加到<code>epoll</code>对象的文件描述符的数量。从 <code>Linux</code> 内核 <code>2.6.8</code> 版本起，不再需要这个参数了（内核不需要该参数就可以动态地调整所需数据结构的大小），但是<code>size</code>仍然必须大于零，以便在旧内核上运行新的<code>epoll</code>应用程序时确保向后兼容性。</li>
</ul>
<p><strong>【返回值】</strong><code>int</code>类型，成功将返回一个<code>epoll</code>句柄，这其实就是一个文件描述符(非负整数)。如果发生错误，则返回<code>-1</code>，并设置<code>errno</code>来表示错误类型。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">define</span> MAX_EVENTS 500</span></span><br><span class="line"><span class="type">int</span> epollFd = <span class="number">-1</span>;</span><br><span class="line">epollFd = epoll_create(MAX_EVENTS);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong>当我们创建好<code>epoll</code>句柄后，它就会占用一个文件描述符，当我们使用完毕后，需要调用<code>close</code>来关闭这个<code>epoll</code>句柄，否则可能会导致<code>fd</code>不足。</p>
<h3 id="1-2-使用实例"><a href="#1-2-使用实例" class="headerlink" title="1.2 使用实例"></a><font size=3>1.2 使用实例</font></h3><p>暂无</p>
<h2 id="2-epoll-ctl"><a href="#2-epoll-ctl" class="headerlink" title="2. epoll_ctl()"></a><font size=3>2. <code>epoll_ctl()</code></font></h2><h3 id="2-1-函数说明"><a href="#2-1-函数说明" class="headerlink" title="2.1 函数说明"></a><font size=3>2.1 函数说明</font></h3><p>在<code>linux</code>下可以使用<code>man 2 epoll_ctl</code>命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">epoll_ctl</span><span class="params">(<span class="type">int</span> epfd, <span class="type">int</span> op, <span class="type">int</span> fd, <span class="keyword">struct</span> epoll_event *event)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数用于控制 <code>epoll</code> 对象，主要涉及 <code>epoll</code> 红黑树上节点的一些操作，比如添加节点，删除节点，修改节点事件。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li><code>epfd</code>：<code>int</code>类型，通过 <code>epoll_create()</code> 创建的 <code>epoll</code> 对象句柄。</li>
<li><code>op</code>：<code>int</code>类型，表示动作类型，是对红黑树的操作，添加节点、删除节点、修改节点事件。</li>
</ul>
<details class="folding-tag" blue><summary> 点击查看 op 可取的值 </summary>
              <div class='content'>
              <table>    <tr><td align="center" width=150px>EPOLL_CTL_ADD</td><td align="left">注册新的 fd 到 epoll 对象中，相当于往红黑树添加一个节点。</td></tr>    <tr><td align="center" width=150px>EPOLL_CTL_MOD</td><td align="left">修改已注册的 fd 的监听事件，相当于把红黑树上监听的 socket 对应的监听事件做修改。</td></tr>    <tr><td align="center" width=150px>EPOLL_CTL_DEL</td><td align="left">从 epoll 对象中删除一个 fd，相当于取消监听 socket 的事件。</td></tr></table>
              </div>
            </details>

<ul>
<li><code>fd</code>：<code>int</code>类型，需要添加监听的 <code>socket</code> 描述符，可以是监听套接字，也可以是与客户端通讯的通讯套接字。</li>
<li><code>event</code>：<code>struct epoll_event</code>类型结构体指针变量，表示事件的信息。</li>
</ul>
<details class="folding-tag" blue><summary> 点击查看 event 参数详细说明 </summary>
              <div class='content'>
              <p>我们在使用<code>man</code>手册的时候，下边会有该参数类型的说明：</p><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">typedef</span> <span class="class"><span class="keyword">union</span> <span class="title">epoll_data</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	<span class="type">void</span>        *ptr;</span><br><span class="line">	<span class="type">int</span>          fd;</span><br><span class="line">	<span class="type">uint32_t</span>     u32;</span><br><span class="line">	<span class="type">uint64_t</span>     u64;</span><br><span class="line">&#125; <span class="type">epoll_data_t</span>;</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">epoll_event</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	<span class="type">uint32_t</span>     events;      <span class="comment">/* Epoll events */</span></span><br><span class="line">	<span class="type">epoll_data_t</span> data;        <span class="comment">/* User data variable */</span></span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure><p><strong>【成员说明】</strong></p><ul><li><code>events</code>：<code>uint32_t</code>类型，代表要监听的 <code>epoll</code> 事件类型，有读事件，写事件等。</li></ul><table>    <tr><td align="center" width=150px>events取值</td><td align="center">含义</td></tr>    <tr><td align="center" width=150px>EPOLLIN</td><td align="left">表示对应的文件描述符可读。例如，如果客户端发送消息过来，代表服务器收到了可读事件。</td></tr>    <tr><td align="center" width=150px>EPOLLOUT</td><td align="left">表示对应的文件描述符可写。如果 fd 对应的发数据内核缓冲区不为满，只要监听了写事件，就会触发可写事件。</td></tr>    <tr><td align="center" width=150px>EPOLLPRI</td><td align="left">表示对应的文件描述符有紧急数据可读（带外数据）。</td></tr>    <tr><td align="center" width=150px>EPOLLERR</td><td align="left">表示对应的文件描述符发生错误。</td></tr>    <tr><td align="center" width=150px>EPOLLHUP</td><td align="left">表示对应的文件描述符被挂起。</td></tr>    <tr><td align="center" width=150px>EPOLLET</td><td align="left">将对应的文件描述符设置为边缘触发（edge-triggered），这是相对于水平触发（level-triggered）而言的。</td></tr>    <tr><td align="center" width=150px>EPOLLRDHUP</td><td align="left">监听套接字关闭或半关闭事件，Linux 内核 2.6.17 后可用。</td></tr></table><ul><li><code>data</code>：<code>epoll_data_t</code>类型，这是一个联合体类型，它可以在我们调用 <code>epoll_ctl</code> 给 <code>fd</code> 添加或者修改描述符监听的事件时附带一些数据。最典型的用法就是每个通讯套接字会对应内存中的一块数据区，这块数据区一般存放着一些连接相关的信息，比如对端的 <code>IP</code>，端口等。当我们要添加该通讯套接字监听事件时就可以把这块内存的地址赋值给 <code>ptr</code>，这样当我们调用 <code>epoll_wait</code> 时也可以取出这些信息。</li></ul>
              </div>
            </details>

<p><strong>【返回值】</strong><code>int</code>类型，成功返回<code>0</code>；失败返回<code>-1</code>，并设置<code>errno</code>来表示错误类型。</p>
<p><strong>【使用格式】</strong>一般情况基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">epoll_event</span> <span class="title">event</span>;</span>      <span class="comment">/* 定义epoll事件 */</span></span><br><span class="line">epfd = epoll_create(<span class="number">1</span>);        <span class="comment">/* 创建epoll对象 */</span></span><br><span class="line"></span><br><span class="line">event.data.fd = socket_fd;     <span class="comment">/* 填充事件的 fd */</span></span><br><span class="line">event.events = EPOLLIN;        <span class="comment">/* 填充事件类型 */</span></span><br><span class="line">epoll_ctl(epfd, EPOLL_CTL_ADD, socket_fd, &amp;event);<span class="comment">/* 把socket_fd 添加到epoll中 */</span></span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong><code>none</code></p>
<h3 id="2-2-使用实例"><a href="#2-2-使用实例" class="headerlink" title="2.2 使用实例"></a><font size=3>2.2 使用实例</font></h3><p>暂无</p>
<h2 id="3-epoll-wait"><a href="#3-epoll-wait" class="headerlink" title="3. epoll_wait()"></a><font size=3>3. <code>epoll_wait()</code></font></h2><h3 id="3-1-函数说明"><a href="#3-1-函数说明" class="headerlink" title="3.1 函数说明"></a><font size=3>3.1 函数说明</font></h3><p>在<code>linux</code>下可以使用<code>man 2 epoll_wait</code>命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">epoll_wait</span><span class="params">(<span class="type">int</span> epfd, <span class="keyword">struct</span> epoll_event *events, <span class="type">int</span> maxevents, <span class="type">int</span> timeout)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数用于等待事件发生，返回事件集合，也就是获取内核的事件通知。其实就是遍历双向链表，把双向链表里的节点数据拷贝出来，拷贝完毕后就从双向链表移除。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li><p><code>epfd</code>：<code>int</code>类型，通过 <code>epoll_create()</code> 创建的 <code>epoll</code> 对象句柄。</p>
</li>
<li><p><code>events</code>：<code>struct epoll_event</code>类型结构体指针变量，这是一个传出参数，用于获取从内核传出的已经符合用户要求的事件集合，一般这里我们会定义一个<code>struct epoll_event</code>结构体数组，并将数组首地址赋值给该变量。</p>
</li>
<li><p><code>maxevents</code>：<code>int</code>类型，代表可以存放的事件个数，就是每次可以处理的最大事件数，也就是<code>events</code>数组的大小。注意这个值要大于<code>0</code>，并且在以前的时候不能大于<code>epoll_create()</code>中参数<code>size</code>的大小，后来<code>epoll_create()</code>忽略<code>size</code>参数后，好像就没有这个限制了。</p>
</li>
<li><p><code>timeout</code>：<code>int</code>类型，表示超时时间，单位为毫秒（<code>ms</code>）。</p>
</li>
</ul>
<details class="folding-tag" blue><summary> 点击查看 timeout 取值说明 </summary>
              <div class='content'>
              <table>    <tr><td align="center" width=150px>timeout = 0   </td><td align="left">立即返回</td></tr>    <tr><td align="center" width=150px>timeout = -1  </td><td align="left">阻塞等待</td></tr>    <tr><td align="center" width=150px>timeout &gt; 0</td><td align="left">超时后返回</td></tr></table>
              </div>
            </details>

<p><strong>【返回值】</strong><code>int</code>类型，可能会有。以下三种情况：</p>
<ul>
<li>返回<code>-1</code>：表示发生错误，并会设置<code>errno</code>表示错误类型。</li>
<li>返回<code>0</code>：超时时间<code>timeout</code>到了，但是监听的事件中依然没有符合我们要求的事件发生。</li>
<li>返回正整数：表示符合我们要求的事件发生了，返回值代表这些事件的个数。</li>
</ul>
<p><strong>【使用格式】</strong>一般情况基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line">epret = epoll_wait(epfd, events, <span class="number">20</span>, <span class="number">-1</span>); <span class="comment">/* 开始监听事件 */</span></span><br><span class="line"><span class="keyword">if</span>(epret &lt; <span class="number">0</span>)</span><br><span class="line">&#123;</span><br><span class="line">	perror(<span class="string">&quot;epoll_wait error&quot;</span>);</span><br><span class="line">	<span class="keyword">continue</span>;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">for</span>(i = <span class="number">0</span>; i &lt; epret; i++) <span class="comment">/* 查询事件并处理 */</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="comment">/* 如果事件的fd是监听的accept等待连接的socket fd 说明有客户端连接 */</span></span><br><span class="line">	<span class="keyword">if</span>(events[i].data.fd == socket_fd)</span><br><span class="line">	&#123;</span><br><span class="line">		...</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">else</span> <span class="comment">/* 其他情况的话就是数据的处理 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		...</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>



<p><strong>【注意事项】</strong><code>none</code></p>
<h3 id="3-2-使用实例"><a href="#3-2-使用实例" class="headerlink" title="3.2 使用实例"></a><font size=3>3.2 使用实例</font></h3><p>暂无</p>
<h2 id="4-epoll-pwait"><a href="#4-epoll-pwait" class="headerlink" title="4. epoll_pwait()"></a><font size=3>4. <code>epoll_pwait()</code></font></h2><h3 id="4-1-函数说明"><a href="#4-1-函数说明" class="headerlink" title="4.1 函数说明"></a><font size=3>4.1 函数说明</font></h3><p>在<code>linux</code>下可以使用<code>man 2 epoll_pwait</code>命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">epoll_pwait</span><span class="params">(<span class="type">int</span> epfd, <span class="keyword">struct</span> epoll_event *events, <span class="type">int</span> maxevents, <span class="type">int</span> timeout, <span class="type">const</span> <span class="type">sigset_t</span> *sigmask)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数与<code>epoll_wait()</code>一样,只是多了一个信号掩码的参数，是一个<strong>防止信号干扰的增强型</strong> <code>epoll_wait()</code>函数。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li><p><code>epfd</code>：<code>int</code>类型，通过 <code>epoll_create()</code> 创建的 <code>epoll</code> 对象句柄。</p>
</li>
<li><p><code>events</code>：<code>struct epoll_event</code>类型结构体指针变量，这是一个传出参数，用于获取从内核传出的已经符合用户要求的事件集合。</p>
</li>
<li><p><code>maxevents</code>：<code>int</code>类型，代表可以存放的事件个数，就是每次可以处理的最大事件数，也就是<code>events</code>数组的大小。注意这个值要大于<code>0</code>，并且不能大于<code>epoll_create()</code>中参数<code>size</code>的大小。</p>
</li>
<li><p><code>timeout</code>：<code>int</code>类型，表示超时时间，单位为毫秒（<code>ms</code>）。</p>
</li>
</ul>
<details class="folding-tag" blue><summary> 点击查看 timeout 取值说明 </summary>
              <div class='content'>
              <table>    <tr><td align="center" width=150px>timeout = 0   </td><td align="left">立即返回</td></tr>    <tr><td align="center" width=150px>timeout = -1  </td><td align="left">阻塞等待</td></tr>    <tr><td align="center" width=150px>timeout &gt; 0</td><td align="left">超时后返回</td></tr></table>
              </div>
            </details>

<ul>
<li><code>sigmask</code>：<code>sigset_t</code>类型，表示信号掩码，指定一个需要屏蔽的信号集，当该参数为<code>NULL</code>时，该函数就等价于<code>epoll_wait()</code>。</li>
</ul>
<p><strong>【返回值】</strong><code>int</code>类型，可能会有。以下三种情况：</p>
<ul>
<li>返回<code>-1</code>：表示发生错误，并会设置<code>errno</code>表示错误类型。</li>
<li>返回<code>0</code>：超时时间<code>timeout</code>到了，但是监听的事件中依然没有符合我们要求的事件发生。</li>
<li>返回正整数：表示符合我们要求的事件发生了，返回值代表这些事件的个数。</li>
</ul>
<p><strong>【使用格式】</strong><code>none</code></p>
<p><strong>【注意事项】</strong><code>none</code></p>
<h3 id="4-2-使用实例"><a href="#4-2-使用实例" class="headerlink" title="4.2 使用实例"></a><font size=3>4.2 使用实例</font></h3><p>暂无</p>
<h1 id="四、工作模式"><a href="#四、工作模式" class="headerlink" title="四、工作模式"></a><font size=3>四、工作模式</font></h1><p><code>epoll</code>对文件描述符的操作有两种模式：<code>LT</code>（<code>level trigger</code>）和<code>ET</code>（<code>edge trigger</code>），其中<code>LT</code>模式是默认模式。</p>
<ul>
<li><code>LT</code>模式</li>
</ul>
<p><code>LT</code>（<code>Level Triggered</code>），水平触发模式。该模式为<code>epoll</code>的默认工作模式，它同时支持阻塞和非阻塞的<code>socket</code>。在该种模式下，当<code>epoll_wait</code>检测到描述符事件发生并将此事件通知进程，进程可以不立即处理该事件，当下次调用<code>epoll_wait</code>时，会再次响应进程并通知此事件，直到该事件被进程处理。在后边的例子中，当数据不被处理的话，可能会导致<code>epoll_wait()</code>函数不再阻塞，从而一直通知进程有新数据到达。</p>
<ul>
<li><code>ET</code>模式</li>
</ul>
<p><code>ET</code>（<code>Edge Triggered</code>），边缘触发模式。该模式是一种高速处理模式，当且仅当状态发生变化时进程才会获得通知。当<code>epoll_wait</code>检测到描述符事件发生并将此事件通知进程，进程必须立即处理该事件，如果不处理，或者只是处理了一部分的数据，并没有全部处理，那么下次调用<code>epoll_wait</code>时，不会再次响应进程并通知此事件。需要注意的是，每个使用<code>ET</code>模式的文件描述符都应该是非阻塞的，如果文件描述符是阻塞的，那么读或写操作将会因为没有后续的事件而一直处于阻塞状态（饥渴状态）。</p>
<blockquote>
<p>ET模式在很大程度上减少了 epoll 事件被重复触发的次数，因此效率要比 LT 模式高。但是需要注意 epoll 工作在 ET 模式的时候，必须使用非阻塞套接口，以避免由于一个文件句柄的阻塞读&#x2F;阻塞写操作把处理多个文件描述符的任务饿死。</p>
</blockquote>
<h1 id="五、使用实例"><a href="#五、使用实例" class="headerlink" title="五、使用实例"></a><font size=3>五、使用实例</font></h1><p>下边的程序中，我只在<code>server</code>中使用了<code>epoll</code>，客户端的程序使用的还是<code>select</code>。</p>
<h2 id="1-基本使用实例"><a href="#1-基本使用实例" class="headerlink" title="1. 基本使用实例"></a><font size=3>1. 基本使用实例</font></h2><h3 id="1-1-server服务器端"><a href="#1-1-server服务器端" class="headerlink" title="1.1 server服务器端"></a><font size=3>1.1 <code>server</code>服务器端</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span 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class="comment"> * Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"> * File name: server.c</span></span><br><span class="line"><span class="comment"> * Author   : fanhua</span></span><br><span class="line"><span class="comment"> * Description: server服务器端——epoll(TCP)</span></span><br><span class="line"><span class="comment"> * ======================================================</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="comment">/* 头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span>      <span class="comment">/* perror */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span>     <span class="comment">/* exit atoi */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;errno.h&gt;</span>      <span class="comment">/* errno号 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/types.h&gt;</span>  <span class="comment">/* socket           bind listen accept send */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/socket.h&gt;</span> <span class="comment">/* socket inet_addr bind listen accept send */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;strings.h&gt;</span>    <span class="comment">/* bzero */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;arpa/inet.h&gt;</span>  <span class="comment">/* htons  inet_addr inet_pton */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;netinet/in.h&gt;</span> <span class="comment">/* ntohs  inet_addr inet_ntop*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span>     <span class="comment">/* close */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span>     <span class="comment">/* strlen strcat*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span> <span class="comment">/* epoll_create epoll_ctl epoll_wait */</span></span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span>; <span class="comment">/* 提示信息打印函数 */</span></span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="comment">/* 参数判断及端口号处理 */</span></span><br><span class="line">	<span class="type">int</span> port = <span class="number">-1</span>;</span><br><span class="line">	<span class="keyword">if</span> (argc != <span class="number">3</span>)<span class="comment">/* 参数数量不对时打印提示信息 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	port = atoi(argv[<span class="number">2</span>]);<span class="comment">/* 字符串转数字 */</span></span><br><span class="line">	<span class="keyword">if</span> (port &lt; <span class="number">5000</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 1.创建套接字，得到socket描述符 */</span></span><br><span class="line">	<span class="type">int</span> socket_fd = <span class="number">-1</span>; <span class="comment">/* 接收服务器端socket描述符 */</span></span><br><span class="line">	<span class="keyword">if</span>((socket_fd = socket(AF_INET, SOCK_STREAM, <span class="number">0</span>)) &lt; <span class="number">0</span>)<span class="comment">/* SOCK_STREAM,使用TCP协议 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;socket&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 允许绑定地址快速重用 */</span></span><br><span class="line">	<span class="type">int</span> b_reuse = <span class="number">1</span>;</span><br><span class="line">	setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &amp;b_reuse, <span class="keyword">sizeof</span> (<span class="type">int</span>));</span><br><span class="line">	<span class="comment">/* 2.将套接字与指定端口号和IP进行绑定 */</span></span><br><span class="line">	<span class="comment">/* 2.1填充struct sockaddr_in结构体变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sin</span>;</span></span><br><span class="line">	bzero (&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span> (<span class="built_in">sin</span>));  <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_family = AF_INET;    <span class="comment">/* 协议族, IPv4 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_port = htons(port);  <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;<span class="built_in">sin</span>.sin_addr) != <span class="number">1</span>)<span class="comment">/* 填充IP地址,INADDR_ANY表示允许监听任意IP,但是它其实是(in_addr_t) 0x00000000 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 2.2绑定 */</span></span><br><span class="line">	<span class="keyword">if</span>(bind(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span>(<span class="built_in">sin</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;bind&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/*3.调用listen()把主动套接字变成被动套接字 */</span></span><br><span class="line">	<span class="keyword">if</span> (listen(socket_fd, <span class="number">5</span>) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;listen&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;Server starting....OK!\n&quot;</span>);</span><br><span class="line">	<span class="comment">/*4.阻塞等待客户端连接请求相关变量定义 */</span></span><br><span class="line">	<span class="type">int</span> client_fd = <span class="number">-1</span>;</span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">cin</span>;</span>          <span class="comment">/* 用于存储成功连接的客户端的IP信息 */</span></span><br><span class="line">	<span class="type">socklen_t</span> addrlen = <span class="keyword">sizeof</span>(<span class="built_in">cin</span>);</span><br><span class="line">	<span class="comment">/* 5.打印成功连接的客户端的信息相关变量定义 */</span></span><br><span class="line">	<span class="type">char</span> ipv4_addr[<span class="number">16</span>];</span><br><span class="line">	<span class="comment">/* 6.数据读写相关变量定义 */</span></span><br><span class="line">	<span class="type">int</span> ret = <span class="number">-1</span>;</span><br><span class="line">	<span class="type">char</span> buf[BUFSIZ]; <span class="comment">/* BUFSIZ是在stdio.h中定义的一个宏，值为8192 */</span></span><br><span class="line">	<span class="type">char</span> replay[BUFSIZ];</span><br><span class="line">	<span class="comment">/* 7.epoll实现多路复用相关变量定义 */</span></span><br><span class="line">	<span class="type">int</span> epfd, epret, i;</span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">epoll_event</span> <span class="title">event</span>;</span>      <span class="comment">/* 定义epoll事件 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">epoll_event</span> <span class="title">events</span>[20];</span> <span class="comment">/* 定义epoll事件集合 */</span></span><br><span class="line">	epfd = epoll_create(<span class="number">1</span>);        <span class="comment">/* 创建epoll对象 */</span></span><br><span class="line"></span><br><span class="line">	event.data.fd = socket_fd;     <span class="comment">/* 填充事件的 fd */</span></span><br><span class="line">	event.events = EPOLLIN;        <span class="comment">/* 填充事件类型 */</span></span><br><span class="line">	epoll_ctl(epfd, EPOLL_CTL_ADD, socket_fd, &amp;event);<span class="comment">/* 把socket_fd 添加到epoll中 */</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 8.数据处理 */</span></span><br><span class="line">	<span class="keyword">while</span>(<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="comment">/* 开始监听事件 */</span></span><br><span class="line">		epret = epoll_wait(epfd, events, <span class="number">20</span>, <span class="number">-1</span>);</span><br><span class="line">		<span class="keyword">if</span>(epret &lt; <span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;epoll_wait error&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 查询事件并处理 */</span></span><br><span class="line">		<span class="keyword">for</span>(i = <span class="number">0</span>; i &lt; epret; i++)</span><br><span class="line">		&#123;</span><br><span class="line">			<span class="comment">/* 如果事件的fd是监听的accept等待连接的socket fd 说明有客户端连接 */</span></span><br><span class="line">			<span class="keyword">if</span>(events[i].data.fd == socket_fd)</span><br><span class="line">			&#123;</span><br><span class="line">				<span class="keyword">if</span> ((client_fd = accept(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">cin</span>, &amp;addrlen)) &lt; <span class="number">0</span>)</span><br><span class="line">				&#123;</span><br><span class="line">					perror(<span class="string">&quot;accept&quot;</span>);</span><br><span class="line">					<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">				&#125;</span><br><span class="line">				event.data.fd = client_fd;        <span class="comment">/* 填充事件的 fd */</span></span><br><span class="line">				event.events = EPOLLIN | EPOLLET; <span class="comment">/* 填充事件类型 */</span></span><br><span class="line">				epoll_ctl(epfd, EPOLL_CTL_ADD, client_fd, &amp;event);<span class="comment">/* 把socket_fd 添加到epoll中 */</span></span><br><span class="line">				<span class="keyword">if</span> (!inet_ntop(AF_INET, (<span class="type">void</span> *)&amp;<span class="built_in">cin</span>.sin_addr, ipv4_addr, <span class="keyword">sizeof</span>(<span class="built_in">cin</span>)))</span><br><span class="line">				&#123;</span><br><span class="line">					perror (<span class="string">&quot;inet_ntop&quot;</span>);</span><br><span class="line">					<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">				&#125;</span><br><span class="line">				<span class="built_in">printf</span> (<span class="string">&quot;Clinet(%s:%d) is connected successfully![client_fd=%d]\n&quot;</span>, ipv4_addr, ntohs(<span class="built_in">cin</span>.sin_port), client_fd);</span><br><span class="line"></span><br><span class="line">			&#125;</span><br><span class="line">			<span class="keyword">else</span> <span class="comment">/* 其他情况的话就是数据的处理 */</span></span><br><span class="line">			&#123;</span><br><span class="line">				bzero(buf, BUFSIZ);</span><br><span class="line">				bzero(replay, BUFSIZ);</span><br><span class="line">				<span class="keyword">do</span>&#123;</span><br><span class="line">					ret = read(events[i].data.fd, buf, BUFSIZ - <span class="number">1</span>);</span><br><span class="line">				&#125;<span class="keyword">while</span>(ret &lt; <span class="number">0</span> &amp;&amp; EINTR == errno);</span><br><span class="line">				<span class="keyword">if</span>(ret &lt; <span class="number">0</span>)</span><br><span class="line">				&#123;</span><br><span class="line">					perror(<span class="string">&quot;read&quot;</span>);</span><br><span class="line">					<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">				&#125;</span><br><span class="line">				<span class="keyword">if</span>(!ret) <span class="comment">/* 对方已经关闭，客户端断开 */</span></span><br><span class="line">				&#123;</span><br><span class="line">					close(events[i].data.fd);</span><br><span class="line">					<span class="built_in">printf</span>(<span class="string">&quot;closed client: %d \n&quot;</span>, events[i].data.fd);</span><br><span class="line">					epoll_ctl(epfd, EPOLL_CTL_DEL, events[i].data.fd, &amp;event);<span class="comment">/* 把 events[i].data.fd 从 epoll 中移除 */</span></span><br><span class="line">				&#125;</span><br><span class="line">				<span class="keyword">else</span></span><br><span class="line">				&#123;</span><br><span class="line">					<span class="built_in">printf</span>(<span class="string">&quot;Receive data[client_fd=%d]: %s&quot;</span>, events[i].data.fd, buf);</span><br><span class="line">					<span class="built_in">strcat</span>(replay, buf);</span><br><span class="line">					ret = send(events[i].data.fd, replay, <span class="built_in">strlen</span>(replay), <span class="number">0</span>);</span><br><span class="line">					<span class="keyword">if</span>(ret &lt; <span class="number">0</span>)</span><br><span class="line">					&#123;</span><br><span class="line">						perror(<span class="string">&quot;send&quot;</span>);</span><br><span class="line">						<span class="keyword">continue</span>;</span><br><span class="line">					&#125;</span><br><span class="line">				&#125;</span><br><span class="line">			&#125;</span><br><span class="line">		&#125;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 9.关闭文件描述符 */</span></span><br><span class="line">	close(socket_fd);</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * @Function: usage</span></span><br><span class="line"><span class="comment"> * @Description: 用户提示信息打印函数</span></span><br><span class="line"><span class="comment"> * @param str : 当前应用程序命令字符串，一般是./app</span></span><br><span class="line"><span class="comment"> * @return  : none</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n%s serv_ip serv_port&quot;</span>, str);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_ip: server ip address&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_port: server port(&gt;5000)\n\n&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t Attention: The IP address must be the IP address of the local nic or 0.0.0.0 \n\n&quot;</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="1-2-client客户端"><a href="#1-2-client客户端" class="headerlink" title="1.2 client客户端"></a><font size=3>1.2 <code>client</code>客户端</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
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class="line">151</span><br><span class="line">152</span><br><span class="line">153</span><br><span class="line">154</span><br><span class="line">155</span><br><span class="line">156</span><br><span class="line">157</span><br><span class="line">158</span><br><span class="line">159</span><br><span class="line">160</span><br><span class="line">161</span><br><span class="line">162</span><br><span class="line">163</span><br><span class="line">164</span><br><span class="line">165</span><br><span class="line">166</span><br><span class="line">167</span><br><span class="line">168</span><br><span class="line">169</span><br><span class="line">170</span><br><span class="line">171</span><br><span class="line">172</span><br><span class="line">173</span><br><span class="line">174</span><br><span class="line">175</span><br><span class="line">176</span><br><span class="line">177</span><br><span class="line">178</span><br><span class="line">179</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/** =====================================================</span></span><br><span class="line"><span class="comment"> * Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"> * File name: cilent.c</span></span><br><span class="line"><span class="comment"> * Author   : fanhua</span></span><br><span class="line"><span class="comment"> * Description: client客户端程序——epoll(TCP)</span></span><br><span class="line"><span class="comment"> * ======================================================</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="comment">/* 头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span>     <span class="comment">/* perror fgets */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span>    <span class="comment">/* exit atoi*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;errno.h&gt;</span>     <span class="comment">/* errno号 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span>    <span class="comment">/* write close */</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/types.h&gt;</span> <span class="comment">/* socket           connect send */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/socket.h&gt;</span><span class="comment">/* socket inet_addr connect send */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;netinet/in.h&gt;</span><span class="comment">/* inet_addr */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;arpa/inet.h&gt;</span> <span class="comment">/* inet_addr inet_pton htonl*/</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span>    <span class="comment">/* bzero strncasecmp strlen */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span> <span class="comment">/* epoll_create epoll_ctl epoll_wait */</span></span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span>; <span class="comment">/* 提示信息打印函数 */</span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 主函数 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="comment">/* 参数判断及端口号处理 */</span></span><br><span class="line">	<span class="type">int</span> port = <span class="number">-1</span>;</span><br><span class="line">	<span class="type">int</span> portClient = <span class="number">-1</span>;</span><br><span class="line">	<span class="keyword">if</span> (argc != <span class="number">4</span>)<span class="comment">/* 参数数量不对时打印提示信息 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	port = atoi(argv[<span class="number">2</span>]);<span class="comment">/* 字符串转数字 */</span></span><br><span class="line">	portClient = atoi(argv[<span class="number">3</span>]);</span><br><span class="line">	<span class="keyword">if</span> (port &lt; <span class="number">5000</span> || portClient &lt; <span class="number">5000</span> || (port == portClient))</span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 1.打开套接字，得到套接字描述符 */</span></span><br><span class="line">	<span class="type">int</span> socket_fd = <span class="number">-1</span>; <span class="comment">/* 接收服务器端socket描述符 */</span></span><br><span class="line">	<span class="keyword">if</span> ((socket_fd = socket(AF_INET, SOCK_STREAM, <span class="number">0</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;socket&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 允许绑定地址快速重用 */</span></span><br><span class="line">	<span class="type">int</span> b_reuse = <span class="number">1</span>;</span><br><span class="line">	setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &amp;b_reuse, <span class="keyword">sizeof</span> (<span class="type">int</span>));</span><br><span class="line">	<span class="comment">/* 2.连接服务器 */</span></span><br><span class="line">	<span class="comment">/* 2.1填充struct sockaddr_in结构体变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sin</span>;</span></span><br><span class="line">	bzero (&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span> (<span class="built_in">sin</span>)); <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_family = AF_INET;   <span class="comment">/* 协议族 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_port = htons(port); <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="comment">/* 客户端的 argv[1] 需要与系统的IP一致 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;<span class="built_in">sin</span>.sin_addr) != <span class="number">1</span>)<span class="comment">/* IP地址 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 绑定固定的IP 和 端口号 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sinClient</span>;</span></span><br><span class="line">	bzero(&amp;sinClient, <span class="keyword">sizeof</span> (sinClient)); <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	sinClient.sin_family = AF_INET;   <span class="comment">/* 协议族 */</span></span><br><span class="line">	sinClient.sin_port = htons(portClient); <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;sinClient.sin_addr) != <span class="number">1</span>)<span class="comment">/* IP地址 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">if</span>(bind(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;sinClient, <span class="keyword">sizeof</span>(sinClient)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;bind&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 2.2连接 */</span></span><br><span class="line">	<span class="keyword">if</span>(connect(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span>(<span class="built_in">sin</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;connect&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;Client staring...OK!\n&quot;</span>);</span><br><span class="line">	<span class="comment">/* 3.数据读写相关变量定义 */</span></span><br><span class="line">	<span class="type">int</span> ret = <span class="number">-1</span>;</span><br><span class="line">	<span class="type">char</span> buf[BUFSIZ]; <span class="comment">/* BUFSIZ是在stdio.h中定义的一个宏，值为8192 */</span></span><br><span class="line">	<span class="type">char</span> replay[BUFSIZ];</span><br><span class="line">	<span class="comment">/* 4.select实现多路复用相关变量定义 */</span></span><br><span class="line">	fd_set rset;   <span class="comment">/* 用于检测读状态的文件描述符集 */</span></span><br><span class="line">	<span class="type">int</span> maxfd = <span class="number">-1</span>;<span class="comment">/* 最大文件描述符编号 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">timeval</span> <span class="title">tout</span>;</span><span class="comment">/* 超时时间结构体变量 */</span></span><br><span class="line">	tout.tv_sec = <span class="number">5</span>;   <span class="comment">/* 设置超时时间秒数 */</span></span><br><span class="line">	tout.tv_usec = <span class="number">0</span>;  <span class="comment">/* 设置超时时间微秒数 */</span></span><br><span class="line">	<span class="comment">/* 5.开始数据传输 */</span></span><br><span class="line">	<span class="keyword">while</span> (<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		FD_ZERO(&amp;rset);    <span class="comment">/* 清空文件描述符集 */</span></span><br><span class="line">		FD_SET(<span class="number">0</span>, &amp;rset);  <span class="comment">/* 将文件描述符0(标准输入)添加到文件描述符集 */</span></span><br><span class="line">		FD_SET(socket_fd, &amp;rset); <span class="comment">/* 将用于监听的socket套接字添加到文件描述符集 */</span></span><br><span class="line">		maxfd = socket_fd;        <span class="comment">/* 重置最大文件描述符集大小 */</span></span><br><span class="line">		<span class="comment">/* 5.1开始检测文件描述符 */</span></span><br><span class="line">		ret = select(maxfd + <span class="number">1</span>, &amp;rset, <span class="literal">NULL</span>, <span class="literal">NULL</span>, &amp;tout);</span><br><span class="line">		<span class="keyword">if</span>(ret &lt; <span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;select&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 5.2标准键盘文件描述符就绪时的处理 */</span></span><br><span class="line">		<span class="keyword">if</span>(FD_ISSET(<span class="number">0</span>, &amp;rset))</span><br><span class="line">		&#123;</span><br><span class="line">			bzero(buf, BUFSIZ);<span class="comment">/* 清空buf */</span></span><br><span class="line">			<span class="keyword">do</span>&#123;</span><br><span class="line">				ret = read(<span class="number">0</span>, buf, BUFSIZ - <span class="number">1</span>);<span class="comment">/* 从标准输入获取数据 */</span></span><br><span class="line">			&#125;<span class="keyword">while</span>(ret &lt; <span class="number">0</span> &amp;&amp; EINTR == errno);</span><br><span class="line">			<span class="keyword">if</span> (ret &lt; <span class="number">0</span>)<span class="comment">/* 获取数据失败 */</span></span><br><span class="line">			&#123;</span><br><span class="line">				perror (<span class="string">&quot;read() from stdin&quot;</span>);</span><br><span class="line">				<span class="keyword">continue</span>;</span><br><span class="line">			&#125;</span><br><span class="line">			<span class="comment">/* 获取数据成功，但是标准输入中没有数据，不需要写入，继续循环即可 */</span></span><br><span class="line">			<span class="keyword">if</span> (!ret) <span class="keyword">continue</span>;</span><br><span class="line">			<span class="comment">/* 向服务器发送数据 */</span></span><br><span class="line">			<span class="keyword">if</span>(write(socket_fd, buf, <span class="built_in">strlen</span>(buf)) &lt; <span class="number">0</span>)<span class="comment">/* 将从标准输入获取的数据写入到socket 网络套接字中 */</span></span><br><span class="line">			&#123;</span><br><span class="line">				perror (<span class="string">&quot;write to socket error&quot;</span>);</span><br><span class="line">				<span class="keyword">continue</span>;</span><br><span class="line">			&#125;</span><br><span class="line">			<span class="comment">/* 判断是否需要退出 */</span></span><br><span class="line">			<span class="keyword">if</span> (!strncasecmp(buf, <span class="string">&quot;quit&quot;</span>, <span class="built_in">strlen</span> (<span class="string">&quot;quit&quot;</span>)))  	<span class="comment">//用户输入了quit字符</span></span><br><span class="line">			&#123;</span><br><span class="line">				<span class="built_in">printf</span> (<span class="string">&quot;Client is exiting!\n&quot;</span>);</span><br><span class="line">				<span class="keyword">break</span>;</span><br><span class="line">			&#125;</span><br><span class="line">			</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 5.3socket文件描述符就绪时的处理(服务器有数据发送过来) */</span></span><br><span class="line">		<span class="keyword">if</span>(FD_ISSET(socket_fd, &amp;rset))</span><br><span class="line">		&#123;</span><br><span class="line">			bzero (replay, BUFSIZ);</span><br><span class="line">			<span class="keyword">do</span>&#123;</span><br><span class="line">				ret = recv(socket_fd, replay, BUFSIZ, <span class="number">0</span>);</span><br><span class="line">			&#125;<span class="keyword">while</span> (ret &lt; <span class="number">0</span> &amp;&amp; EINTR == errno);</span><br><span class="line">			<span class="keyword">if</span>(ret &lt; <span class="number">0</span>)</span><br><span class="line">			&#123;</span><br><span class="line">				perror(<span class="string">&quot;recv&quot;</span>);</span><br><span class="line">				<span class="keyword">continue</span>;</span><br><span class="line">			&#125;</span><br><span class="line">			<span class="comment">/* 若服务器已关闭，则直接退出客户端 */</span></span><br><span class="line">			<span class="keyword">if</span> (ret == <span class="number">0</span>) <span class="keyword">break</span>;</span><br><span class="line">			<span class="built_in">printf</span>(<span class="string">&quot;server replay:%s&quot;</span>, replay);</span><br><span class="line">			<span class="keyword">if</span> (!strncasecmp(buf, <span class="string">&quot;quit&quot;</span>, <span class="built_in">strlen</span>(<span class="string">&quot;quit&quot;</span>)))</span><br><span class="line">			&#123;</span><br><span class="line">				<span class="built_in">printf</span> (<span class="string">&quot;Sender Client is exiting... ...!\n&quot;</span>);</span><br><span class="line">				<span class="keyword">break</span>;</span><br><span class="line">			&#125;</span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 6.关闭文件描述符 */</span></span><br><span class="line">	close(socket_fd);</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * @Function: usage</span></span><br><span class="line"><span class="comment"> * @Description: 用户提示信息打印函数</span></span><br><span class="line"><span class="comment"> * @param str : 当前应用程序命令字符串，一般是./app</span></span><br><span class="line"><span class="comment"> * @return  : none</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n%s serv_ip serv_port&quot;</span>, str);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_ip: server ip address&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_port: server port(&gt;5000)\n\n&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t client_port: client portClient(&gt;5000 &amp;&amp; !=port )\n\n&quot;</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="1-3-Makefile"><a href="#1-3-Makefile" class="headerlink" title="1.3 Makefile"></a><font size=3>1.3 <code>Makefile</code></font></h3><p>由于需要生成两个可执行程序，自己输命令有些繁琐，这里使用<code>make</code>来进行。</p>
<details class="folding-tag" blue><summary> 点击查看 Makefile 文件 </summary>
              <div class='content'>
              <figure class="highlight makefile"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">## =====================================================</span></span><br><span class="line"><span class="comment"># Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"># File name: Makefile</span></span><br><span class="line"><span class="comment"># Author   : fanhua</span></span><br><span class="line"><span class="comment"># Description: Makefile文件</span></span><br><span class="line"><span class="comment">## ======================================================</span></span><br><span class="line"><span class="comment"># </span></span><br><span class="line">CC = gcc</span><br><span class="line"></span><br><span class="line">DEBUG = -g -O2 -Wall</span><br><span class="line">CFLAGS += <span class="variable">$(DEBUG)</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># 所有.c文件去掉后缀</span></span><br><span class="line">TARGET_LIST = $&#123;patsubst %.c, %, $&#123;wildcard *.c&#125;&#125; </span><br><span class="line">all : <span class="variable">$(TARGET_LIST)</span></span><br><span class="line"></span><br><span class="line">%.o : %.c</span><br><span class="line">	<span class="variable">$(CC)</span> <span class="variable">$(CFLAGS)</span> -c <span class="variable">$&lt;</span> -o <span class="variable">$@</span></span><br><span class="line"></span><br><span class="line"><span class="meta"><span class="keyword">.PHONY</span>: all clean clean_o clean_out</span></span><br><span class="line">clean : clean_o clean_out</span><br><span class="line">	@rm -vf <span class="variable">$(TARGET_LIST)</span> </span><br><span class="line">	</span><br><span class="line">clean_o :</span><br><span class="line">	@rm -vf *.o</span><br><span class="line">	</span><br><span class="line">clean_out :</span><br><span class="line">	@rm -vf *.out</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="1-4-测试结果"><a href="#1-4-测试结果" class="headerlink" title="1.4 测试结果"></a><font size=3>1.4 测试结果</font></h3><p>我们执行以下命令编译链接程序，生成两个可执行文件：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">make</span><br></pre></td></tr></table></figure>

<p>然后会有如下提示，并生成两个可执行文件吗，分别为服务器端程序<code>server</code>和客户端程序<code>client</code>：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc -g -O2 -Wall    client.c   -o client</span><br><span class="line">gcc -g -O2 -Wall    server.c   -o server</span><br></pre></td></tr></table></figure>

<p>对于服务器端，我们执行以下命令启动服务器进程：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">./server 0.0.0.0 5001 # 允许监听所有网卡IP及端口</span><br></pre></td></tr></table></figure>

<p>对于客户端，我们执行以下命令启动客户端进程：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">./client 192.168.10.101 5001 5002 # 连接到本地一块网卡的IP，并设置客户端向外发送数据的端口为5002</span><br><span class="line">./client 192.168.10.101 5001 5003 # 连接到本地一块网卡的IP，并设置客户端向外发送数据的端口为5003</span><br></pre></td></tr></table></figure>

<p>然后我们就会看到如下现象：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/01HQ%E8%AF%BE%E7%A8%8B%E4%BD%93%E7%B3%BB/LV06-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B/LV06-03-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B-07-%E5%A4%9A%E8%B7%AF%E5%A4%8D%E7%94%A8IO-03-epoll/img/image-20220704104311802.png" alt="image-20220704104311802" style="zoom:50%;" />

<p>可以发现我们发送的数据，在客户端都被打印了出来，说明客户端与服务器端可以进行正常通信。</p>
<h2 id="2-工作模式测试"><a href="#2-工作模式测试" class="headerlink" title="2. 工作模式测试"></a><font size=3>2. 工作模式测试</font></h2><p>下边的例子依然只是修改了服务器的代码，我们在启动服务器的时候选择<code>epoll</code>工作模式，并删除服务器端读取数据部分的代码。</p>
<h3 id="2-1-server服务器端"><a href="#2-1-server服务器端" class="headerlink" title="2.1 server服务器端"></a><font size=3>2.1 <code>server</code>服务器端</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
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class="line">151</span><br><span class="line">152</span><br><span class="line">153</span><br><span class="line">154</span><br><span class="line">155</span><br><span class="line">156</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/** =====================================================</span></span><br><span class="line"><span class="comment"> * Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"> * File name: server.c</span></span><br><span class="line"><span class="comment"> * Author   : fanhua</span></span><br><span class="line"><span class="comment"> * Description: server服务器端——epoll(TCP)</span></span><br><span class="line"><span class="comment"> * ======================================================</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="comment">/* 头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span>      <span class="comment">/* perror */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span>     <span class="comment">/* exit atoi */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;errno.h&gt;</span>      <span class="comment">/* errno号 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/types.h&gt;</span>  <span class="comment">/* socket           bind listen accept send */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/socket.h&gt;</span> <span class="comment">/* socket inet_addr bind listen accept send */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;strings.h&gt;</span>    <span class="comment">/* bzero */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;arpa/inet.h&gt;</span>  <span class="comment">/* htons  inet_addr inet_pton */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;netinet/in.h&gt;</span> <span class="comment">/* ntohs  inet_addr inet_ntop*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span>     <span class="comment">/* close */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span>     <span class="comment">/* strlen strcat*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span> <span class="comment">/* epoll_create epoll_ctl epoll_wait */</span></span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span>; <span class="comment">/* 提示信息打印函数 */</span></span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="comment">/* 参数判断及端口号处理 */</span></span><br><span class="line">	<span class="type">int</span> port = <span class="number">-1</span>;</span><br><span class="line">	<span class="keyword">if</span> (argc != <span class="number">3</span>)<span class="comment">/* 参数数量不对时打印提示信息 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	port = atoi(argv[<span class="number">2</span>]);<span class="comment">/* 字符串转数字 */</span></span><br><span class="line">	<span class="keyword">if</span> (port &lt; <span class="number">5000</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 1.创建套接字，得到socket描述符 */</span></span><br><span class="line">	<span class="type">int</span> socket_fd = <span class="number">-1</span>; <span class="comment">/* 接收服务器端socket描述符 */</span></span><br><span class="line">	<span class="keyword">if</span>((socket_fd = socket(AF_INET, SOCK_STREAM, <span class="number">0</span>)) &lt; <span class="number">0</span>)<span class="comment">/* SOCK_STREAM,使用TCP协议 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;socket&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 允许绑定地址快速重用 */</span></span><br><span class="line">	<span class="type">int</span> b_reuse = <span class="number">1</span>;</span><br><span class="line">	setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &amp;b_reuse, <span class="keyword">sizeof</span> (<span class="type">int</span>));</span><br><span class="line">	<span class="comment">/* 2.将套接字与指定端口号和IP进行绑定 */</span></span><br><span class="line">	<span class="comment">/* 2.1填充struct sockaddr_in结构体变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sin</span>;</span></span><br><span class="line">	bzero (&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span> (<span class="built_in">sin</span>));  <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_family = AF_INET;    <span class="comment">/* 协议族, IPv4 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_port = htons(port);  <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;<span class="built_in">sin</span>.sin_addr) != <span class="number">1</span>)<span class="comment">/* 填充IP地址,INADDR_ANY表示允许监听任意IP,但是它其实是(in_addr_t) 0x00000000 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 2.2绑定 */</span></span><br><span class="line">	<span class="keyword">if</span>(bind(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span>(<span class="built_in">sin</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;bind&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/*3.调用listen()把主动套接字变成被动套接字 */</span></span><br><span class="line">	<span class="keyword">if</span> (listen(socket_fd, <span class="number">5</span>) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;listen&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="type">int</span> mode = <span class="number">0</span>;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;please select epoll mode(1:LT 2:ET):&quot;</span>);</span><br><span class="line">	<span class="built_in">scanf</span>(<span class="string">&quot;%d&quot;</span>, &amp;mode);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;Server starting...OK, epoll mode is %d(1:LT 2:ET)!\n&quot;</span>, mode);</span><br><span class="line">	<span class="comment">/*4.阻塞等待客户端连接请求相关变量定义 */</span></span><br><span class="line">	<span class="type">int</span> client_fd = <span class="number">-1</span>;</span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">cin</span>;</span>          <span class="comment">/* 用于存储成功连接的客户端的IP信息 */</span></span><br><span class="line">	<span class="type">socklen_t</span> addrlen = <span class="keyword">sizeof</span>(<span class="built_in">cin</span>);</span><br><span class="line">	<span class="comment">/* 5.打印成功连接的客户端的信息相关变量定义 */</span></span><br><span class="line">	<span class="type">char</span> ipv4_addr[<span class="number">16</span>];</span><br><span class="line">	<span class="comment">/* 6.数据读写相关变量定义 */</span></span><br><span class="line">	<span class="type">int</span> count = <span class="number">0</span>;</span><br><span class="line">	<span class="comment">/* 7.epoll实现多路复用相关变量定义 */</span></span><br><span class="line">	<span class="type">int</span> epfd, epret, i;</span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">epoll_event</span> <span class="title">event</span>;</span>      <span class="comment">/* 定义epoll事件 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">epoll_event</span> <span class="title">events</span>[20];</span> <span class="comment">/* 定义epoll事件集合 */</span></span><br><span class="line">	epfd = epoll_create(<span class="number">1</span>);        <span class="comment">/* 创建epoll对象 */</span></span><br><span class="line"></span><br><span class="line">	event.data.fd = socket_fd;     <span class="comment">/* 填充事件的 fd */</span></span><br><span class="line">	event.events = EPOLLIN;        <span class="comment">/* 填充事件类型 */</span></span><br><span class="line">	epoll_ctl(epfd, EPOLL_CTL_ADD, socket_fd, &amp;event);<span class="comment">/* 把socket_fd 添加到epoll中 */</span></span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 8.数据处理 */</span></span><br><span class="line">	<span class="keyword">while</span>(<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="comment">/* 开始监听事件 */</span></span><br><span class="line">		epret = epoll_wait(epfd, events, <span class="number">20</span>, <span class="number">-1</span>);</span><br><span class="line">		<span class="keyword">if</span>(epret &lt; <span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;epoll_wait error&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 查询事件并处理 */</span></span><br><span class="line">		<span class="keyword">for</span>(i = <span class="number">0</span>; i &lt; epret; i++)</span><br><span class="line">		&#123;</span><br><span class="line">			<span class="comment">/* 如果事件的fd是监听的accept等待连接的socket fd 说明有客户端连接 */</span></span><br><span class="line">			<span class="keyword">if</span>(events[i].data.fd == socket_fd)</span><br><span class="line">			&#123;</span><br><span class="line">				<span class="keyword">if</span> ((client_fd = accept(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">cin</span>, &amp;addrlen)) &lt; <span class="number">0</span>)</span><br><span class="line">				&#123;</span><br><span class="line">					perror(<span class="string">&quot;accept&quot;</span>);</span><br><span class="line">					<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">				&#125;</span><br><span class="line">				event.data.fd = client_fd;        <span class="comment">/* 填充事件的 fd */</span></span><br><span class="line">				<span class="keyword">if</span>(mode == <span class="number">2</span>)</span><br><span class="line">					event.events = EPOLLIN | EPOLLET; <span class="comment">/* ET 模式*/</span></span><br><span class="line">				<span class="keyword">else</span></span><br><span class="line">					event.events = EPOLLIN; <span class="comment">/* LT 模式 */</span></span><br><span class="line">				epoll_ctl(epfd, EPOLL_CTL_ADD, client_fd, &amp;event);<span class="comment">/* 把socket_fd 添加到epoll中 */</span></span><br><span class="line">				<span class="keyword">if</span> (!inet_ntop(AF_INET, (<span class="type">void</span> *)&amp;<span class="built_in">cin</span>.sin_addr, ipv4_addr, <span class="keyword">sizeof</span>(<span class="built_in">cin</span>)))</span><br><span class="line">				&#123;</span><br><span class="line">					perror (<span class="string">&quot;inet_ntop&quot;</span>);</span><br><span class="line">					<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">				&#125;</span><br><span class="line">				<span class="built_in">printf</span> (<span class="string">&quot;Clinet(%s:%d) is connected successfully![client_fd=%d]\n&quot;</span>, ipv4_addr, ntohs(<span class="built_in">cin</span>.sin_port), client_fd);</span><br><span class="line"></span><br><span class="line">			&#125;</span><br><span class="line">			<span class="keyword">else</span> <span class="comment">/* 其他情况的话就是数据的处理,为测试两种模式，这里并不读取数据 */</span></span><br><span class="line">			&#123;</span><br><span class="line">				count++;</span><br><span class="line">				<span class="built_in">printf</span>(<span class="string">&quot;new data arrive!count = %d\n&quot;</span>,count);</span><br><span class="line">				<span class="keyword">if</span>(count &gt; <span class="number">10</span>)</span><br><span class="line">					<span class="built_in">exit</span>(<span class="number">0</span>);</span><br><span class="line">			&#125;</span><br><span class="line">		&#125;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 9.关闭文件描述符 */</span></span><br><span class="line">	close(socket_fd);</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * @Function: usage</span></span><br><span class="line"><span class="comment"> * @Description: 用户提示信息打印函数</span></span><br><span class="line"><span class="comment"> * @param str : 当前应用程序命令字符串，一般是./app</span></span><br><span class="line"><span class="comment"> * @return  : none</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n%s serv_ip serv_port&quot;</span>, str);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_ip: server ip address&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_port: server port(&gt;5000)\n\n&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t Attention: The IP address must be the IP address of the local nic or 0.0.0.0 \n\n&quot;</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="2-2-client客户端"><a href="#2-2-client客户端" class="headerlink" title="2.2 client客户端"></a><font size=3>2.2 <code>client</code>客户端</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
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class="line"><span class="comment">/** =====================================================</span></span><br><span class="line"><span class="comment"> * Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"> * File name: cilent.c</span></span><br><span class="line"><span class="comment"> * Author   : fanhua</span></span><br><span class="line"><span class="comment"> * Description: client客户端程序——epoll(TCP)</span></span><br><span class="line"><span class="comment"> * ======================================================</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="comment">/* 头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span>     <span class="comment">/* perror fgets */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdlib.h&gt;</span>    <span class="comment">/* exit atoi*/</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;errno.h&gt;</span>     <span class="comment">/* errno号 */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span>    <span class="comment">/* write close */</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/types.h&gt;</span> <span class="comment">/* socket           connect send */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/socket.h&gt;</span><span class="comment">/* socket inet_addr connect send */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;netinet/in.h&gt;</span><span class="comment">/* inet_addr */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;arpa/inet.h&gt;</span> <span class="comment">/* inet_addr inet_pton htonl*/</span></span></span><br><span class="line"></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span>    <span class="comment">/* bzero strncasecmp strlen */</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/epoll.h&gt;</span> <span class="comment">/* epoll_create epoll_ctl epoll_wait */</span></span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span>; <span class="comment">/* 提示信息打印函数 */</span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 主函数 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> argc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="comment">/* 参数判断及端口号处理 */</span></span><br><span class="line">	<span class="type">int</span> port = <span class="number">-1</span>;</span><br><span class="line">	<span class="type">int</span> portClient = <span class="number">-1</span>;</span><br><span class="line">	<span class="keyword">if</span> (argc != <span class="number">4</span>)<span class="comment">/* 参数数量不对时打印提示信息 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	port = atoi(argv[<span class="number">2</span>]);<span class="comment">/* 字符串转数字 */</span></span><br><span class="line">	portClient = atoi(argv[<span class="number">3</span>]);</span><br><span class="line">	<span class="keyword">if</span> (port &lt; <span class="number">5000</span> || portClient &lt; <span class="number">5000</span> || (port == portClient))</span><br><span class="line">	&#123;</span><br><span class="line">		usage(argv[<span class="number">0</span>]);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 1.打开套接字，得到套接字描述符 */</span></span><br><span class="line">	<span class="type">int</span> socket_fd = <span class="number">-1</span>; <span class="comment">/* 接收服务器端socket描述符 */</span></span><br><span class="line">	<span class="keyword">if</span> ((socket_fd = socket(AF_INET, SOCK_STREAM, <span class="number">0</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;socket&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 允许绑定地址快速重用 */</span></span><br><span class="line">	<span class="type">int</span> b_reuse = <span class="number">1</span>;</span><br><span class="line">	setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &amp;b_reuse, <span class="keyword">sizeof</span> (<span class="type">int</span>));</span><br><span class="line">	<span class="comment">/* 2.连接服务器 */</span></span><br><span class="line">	<span class="comment">/* 2.1填充struct sockaddr_in结构体变量 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sin</span>;</span></span><br><span class="line">	bzero (&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span> (<span class="built_in">sin</span>)); <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_family = AF_INET;   <span class="comment">/* 协议族 */</span></span><br><span class="line">	<span class="built_in">sin</span>.sin_port = htons(port); <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="comment">/* 客户端的 argv[1] 需要与系统的IP一致 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;<span class="built_in">sin</span>.sin_addr) != <span class="number">1</span>)<span class="comment">/* IP地址 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 绑定固定的IP 和 端口号 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sockaddr_in</span> <span class="title">sinClient</span>;</span></span><br><span class="line">	bzero(&amp;sinClient, <span class="keyword">sizeof</span> (sinClient)); <span class="comment">/* 将内存块（字符串）的前n个字节清零 */</span></span><br><span class="line">	sinClient.sin_family = AF_INET;   <span class="comment">/* 协议族 */</span></span><br><span class="line">	sinClient.sin_port = htons(portClient); <span class="comment">/* 网络字节序的端口号 */</span></span><br><span class="line">	<span class="keyword">if</span>(inet_pton(AF_INET, argv[<span class="number">1</span>], (<span class="type">void</span> *)&amp;sinClient.sin_addr) != <span class="number">1</span>)<span class="comment">/* IP地址 */</span></span><br><span class="line">	&#123;</span><br><span class="line">		perror (<span class="string">&quot;inet_pton&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">if</span>(bind(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;sinClient, <span class="keyword">sizeof</span>(sinClient)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;bind&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 2.2连接 */</span></span><br><span class="line">	<span class="keyword">if</span>(connect(socket_fd, (<span class="keyword">struct</span> sockaddr *)&amp;<span class="built_in">sin</span>, <span class="keyword">sizeof</span>(<span class="built_in">sin</span>)) &lt; <span class="number">0</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;connect&quot;</span>);</span><br><span class="line">		<span class="built_in">exit</span>(<span class="number">-1</span>);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;Client staring...OK!\n&quot;</span>);</span><br><span class="line">	<span class="comment">/* 3.数据读写相关变量定义 */</span></span><br><span class="line">	<span class="type">int</span> ret = <span class="number">-1</span>;</span><br><span class="line">	<span class="type">char</span> buf[BUFSIZ]; <span class="comment">/* BUFSIZ是在stdio.h中定义的一个宏，值为8192 */</span></span><br><span class="line">	<span class="type">char</span> replay[BUFSIZ];</span><br><span class="line">	<span class="comment">/* 4.select实现多路复用相关变量定义 */</span></span><br><span class="line">	fd_set rset;   <span class="comment">/* 用于检测读状态的文件描述符集 */</span></span><br><span class="line">	<span class="type">int</span> maxfd = <span class="number">-1</span>;<span class="comment">/* 最大文件描述符编号 */</span></span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">timeval</span> <span class="title">tout</span>;</span><span class="comment">/* 超时时间结构体变量 */</span></span><br><span class="line">	tout.tv_sec = <span class="number">5</span>;   <span class="comment">/* 设置超时时间秒数 */</span></span><br><span class="line">	tout.tv_usec = <span class="number">0</span>;  <span class="comment">/* 设置超时时间微秒数 */</span></span><br><span class="line">	<span class="comment">/* 5.开始数据传输 */</span></span><br><span class="line">	<span class="keyword">while</span> (<span class="number">1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		FD_ZERO(&amp;rset);    <span class="comment">/* 清空文件描述符集 */</span></span><br><span class="line">		FD_SET(<span class="number">0</span>, &amp;rset);  <span class="comment">/* 将文件描述符0(标准输入)添加到文件描述符集 */</span></span><br><span class="line">		FD_SET(socket_fd, &amp;rset); <span class="comment">/* 将用于监听的socket套接字添加到文件描述符集 */</span></span><br><span class="line">		maxfd = socket_fd;        <span class="comment">/* 重置最大文件描述符集大小 */</span></span><br><span class="line">		<span class="comment">/* 5.1开始检测文件描述符 */</span></span><br><span class="line">		ret = select(maxfd + <span class="number">1</span>, &amp;rset, <span class="literal">NULL</span>, <span class="literal">NULL</span>, &amp;tout);</span><br><span class="line">		<span class="keyword">if</span>(ret &lt; <span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			perror(<span class="string">&quot;select&quot;</span>);</span><br><span class="line">			<span class="keyword">continue</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 5.2标准键盘文件描述符就绪时的处理 */</span></span><br><span class="line">		<span class="keyword">if</span>(FD_ISSET(<span class="number">0</span>, &amp;rset))</span><br><span class="line">		&#123;</span><br><span class="line">			bzero(buf, BUFSIZ);<span class="comment">/* 清空buf */</span></span><br><span class="line">			<span class="keyword">do</span>&#123;</span><br><span class="line">				ret = read(<span class="number">0</span>, buf, BUFSIZ - <span class="number">1</span>);<span class="comment">/* 从标准输入获取数据 */</span></span><br><span class="line">			&#125;<span class="keyword">while</span>(ret &lt; <span class="number">0</span> &amp;&amp; EINTR == errno);</span><br><span class="line">			<span class="keyword">if</span> (ret &lt; <span class="number">0</span>)<span class="comment">/* 获取数据失败 */</span></span><br><span class="line">			&#123;</span><br><span class="line">				perror (<span class="string">&quot;read() from stdin&quot;</span>);</span><br><span class="line">				<span class="keyword">continue</span>;</span><br><span class="line">			&#125;</span><br><span class="line">			<span class="comment">/* 获取数据成功，但是标准输入中没有数据，不需要写入，继续循环即可 */</span></span><br><span class="line">			<span class="keyword">if</span> (!ret) <span class="keyword">continue</span>;</span><br><span class="line">			<span class="comment">/* 向服务器发送数据 */</span></span><br><span class="line">			<span class="keyword">if</span>(write(socket_fd, buf, <span class="built_in">strlen</span>(buf)) &lt; <span class="number">0</span>)<span class="comment">/* 将从标准输入获取的数据写入到socket 网络套接字中 */</span></span><br><span class="line">			&#123;</span><br><span class="line">				perror (<span class="string">&quot;write to socket error&quot;</span>);</span><br><span class="line">				<span class="keyword">continue</span>;</span><br><span class="line">			&#125;</span><br><span class="line">			<span class="comment">/* 判断是否需要退出 */</span></span><br><span class="line">			<span class="keyword">if</span> (!strncasecmp(buf, <span class="string">&quot;quit&quot;</span>, <span class="built_in">strlen</span> (<span class="string">&quot;quit&quot;</span>)))  	<span class="comment">//用户输入了quit字符</span></span><br><span class="line">			&#123;</span><br><span class="line">				<span class="built_in">printf</span> (<span class="string">&quot;Client is exiting!\n&quot;</span>);</span><br><span class="line">				<span class="keyword">break</span>;</span><br><span class="line">			&#125;</span><br><span class="line">			</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="comment">/* 5.3socket文件描述符就绪时的处理(服务器有数据发送过来) */</span></span><br><span class="line">		<span class="keyword">if</span>(FD_ISSET(socket_fd, &amp;rset))</span><br><span class="line">		&#123;</span><br><span class="line">			bzero (replay, BUFSIZ);</span><br><span class="line">			<span class="keyword">do</span>&#123;</span><br><span class="line">				ret = recv(socket_fd, replay, BUFSIZ, <span class="number">0</span>);</span><br><span class="line">			&#125;<span class="keyword">while</span> (ret &lt; <span class="number">0</span> &amp;&amp; EINTR == errno);</span><br><span class="line">			<span class="keyword">if</span>(ret &lt; <span class="number">0</span>)</span><br><span class="line">			&#123;</span><br><span class="line">				perror(<span class="string">&quot;recv&quot;</span>);</span><br><span class="line">				<span class="keyword">continue</span>;</span><br><span class="line">			&#125;</span><br><span class="line">			<span class="comment">/* 若服务器已关闭，则直接退出客户端 */</span></span><br><span class="line">			<span class="keyword">if</span> (ret == <span class="number">0</span>) <span class="keyword">break</span>;</span><br><span class="line">			<span class="built_in">printf</span>(<span class="string">&quot;server replay:%s&quot;</span>, replay);</span><br><span class="line">			<span class="keyword">if</span> (!strncasecmp(buf, <span class="string">&quot;quit&quot;</span>, <span class="built_in">strlen</span>(<span class="string">&quot;quit&quot;</span>)))</span><br><span class="line">			&#123;</span><br><span class="line">				<span class="built_in">printf</span> (<span class="string">&quot;Sender Client is exiting... ...!\n&quot;</span>);</span><br><span class="line">				<span class="keyword">break</span>;</span><br><span class="line">			&#125;</span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="comment">/* 6.关闭文件描述符 */</span></span><br><span class="line">	close(socket_fd);</span><br><span class="line"></span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * @Function: usage</span></span><br><span class="line"><span class="comment"> * @Description: 用户提示信息打印函数</span></span><br><span class="line"><span class="comment"> * @param str : 当前应用程序命令字符串，一般是./app</span></span><br><span class="line"><span class="comment"> * @return  : none</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="type">void</span> <span class="title function_">usage</span><span class="params">(<span class="type">char</span> *str)</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n%s serv_ip serv_port&quot;</span>, str);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_ip: server ip address&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t serv_port: server port(&gt;5000)\n\n&quot;</span>);</span><br><span class="line">	<span class="built_in">printf</span> (<span class="string">&quot;\n\t client_port: client portClient(&gt;5000 &amp;&amp; !=port )\n\n&quot;</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="2-3-Makefile"><a href="#2-3-Makefile" class="headerlink" title="2.3 Makefile"></a><font size=3>2.3 <code>Makefile</code></font></h3><p>由于需要生成两个可执行程序，自己输命令有些繁琐，这里使用<code>make</code>来进行。</p>
<details class="folding-tag" blue><summary> 点击查看 Makefile 文件 </summary>
              <div class='content'>
              <figure class="highlight makefile"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">## =====================================================</span></span><br><span class="line"><span class="comment"># Copyright © hk. 2022-2022. All rights reserved.</span></span><br><span class="line"><span class="comment"># File name: Makefile</span></span><br><span class="line"><span class="comment"># Author   : fanhua</span></span><br><span class="line"><span class="comment"># Description: Makefile文件</span></span><br><span class="line"><span class="comment">## ======================================================</span></span><br><span class="line"><span class="comment"># </span></span><br><span class="line">CC = gcc</span><br><span class="line"></span><br><span class="line">DEBUG = -g -O2 -Wall</span><br><span class="line">CFLAGS += <span class="variable">$(DEBUG)</span></span><br><span class="line"></span><br><span class="line"><span class="comment"># 所有.c文件去掉后缀</span></span><br><span class="line">TARGET_LIST = $&#123;patsubst %.c, %, $&#123;wildcard *.c&#125;&#125; </span><br><span class="line">all : <span class="variable">$(TARGET_LIST)</span></span><br><span class="line"></span><br><span class="line">%.o : %.c</span><br><span class="line">	<span class="variable">$(CC)</span> <span class="variable">$(CFLAGS)</span> -c <span class="variable">$&lt;</span> -o <span class="variable">$@</span></span><br><span class="line"></span><br><span class="line"><span class="meta"><span class="keyword">.PHONY</span>: all clean clean_o clean_out</span></span><br><span class="line">clean : clean_o clean_out</span><br><span class="line">	@rm -vf <span class="variable">$(TARGET_LIST)</span> </span><br><span class="line">	</span><br><span class="line">clean_o :</span><br><span class="line">	@rm -vf *.o</span><br><span class="line">	</span><br><span class="line">clean_out :</span><br><span class="line">	@rm -vf *.out</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h3 id="2-4-测试结果"><a href="#2-4-测试结果" class="headerlink" title="2.4 测试结果"></a><font size=3>2.4 测试结果</font></h3><p>我们执行以下命令编译链接程序，生成两个可执行文件：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">make</span><br></pre></td></tr></table></figure>

<p>然后会有如下提示，并生成两个可执行文件吗，分别为服务器端程序<code>server</code>和客户端程序<code>client</code>：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc -g -O2 -Wall    client.c   -o client</span><br><span class="line">gcc -g -O2 -Wall    server.c   -o server</span><br></pre></td></tr></table></figure>

<p>对于客户端，我们执行以下命令启动客户端进程：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">./client 192.168.10.101 5001 5002 # 连接到本地一块网卡的IP，并设置客户端向外发送数据的端口为5002</span><br></pre></td></tr></table></figure>

<ul>
<li><code>LT</code>模式启动</li>
</ul>
<p>对于服务器端，我们执行以下命令启动服务器进程：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">./server 0.0.0.0 5001 # 允许监听所有网卡IP及端口</span><br></pre></td></tr></table></figure>

<p>然后会得到以下提示：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">please select epoll mode(1:LT 2:ET):</span><br></pre></td></tr></table></figure>

<p>我们选择输入<code>1</code>并按下<code>enter</code>后，服务器端中用于通信的文件描述符将会使用默认的工作模式，也就是<code>LT</code>模式，此时我们来看一下现象：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/01HQ%E8%AF%BE%E7%A8%8B%E4%BD%93%E7%B3%BB/LV06-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B/LV06-03-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B-07-%E5%A4%9A%E8%B7%AF%E5%A4%8D%E7%94%A8IO-03-epoll/img/image-20220704114023374.png" alt="image-20220704114023374" style="zoom:50%;" />

<p>可以发现我们发送的数据，并没有被读取，而服务器端会一直提醒有数据到达，提醒<code>11</code>次后，程序退出，这是因为我设置了超过<code>10</code>次就结束进程，否则会一直打印一直打印，这也说明了，<code>LT</code>模式下，不处理数据的话，内核会一直通知进行，并且<code>epoll_wait()</code>函数也不再阻塞了。</p>
<ul>
<li><code>ET</code>模式启动</li>
</ul>
<p>对于服务器端，我们执行以下命令启动服务器进程：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">./server 0.0.0.0 5001 # 允许监听所有网卡IP及端口</span><br></pre></td></tr></table></figure>

<p>然后会得到以下提示：</p>
<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">please select epoll mode(1:LT 2:ET):</span><br></pre></td></tr></table></figure>

<p>我们选择输入<code>2</code>并按下<code>enter</code>后，服务器端中用于通信的文件描述符将会使用<code>ET</code>模式，此时我们来看一下现象：</p>
<img data-src="https://fanhua-picture.oss-cn-hangzhou.aliyuncs.com/01%E5%B5%8C%E5%85%A5%E5%BC%8F%E5%BC%80%E5%8F%91/01HQ%E8%AF%BE%E7%A8%8B%E4%BD%93%E7%B3%BB/LV06-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B/LV06-03-%E7%BD%91%E7%BB%9C%E7%BC%96%E7%A8%8B-07-%E5%A4%9A%E8%B7%AF%E5%A4%8D%E7%94%A8IO-03-epoll/img/image-20220704114305589.png" alt="image-20220704114305589" style="zoom:50%;" />

<p>可以发现我们发送的数据，并没有被读取，然后我们发送一次就提示一次，即便数据没有被处理。</p>

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